It is the purpose of this research project to continue to develop experimental designs and methods of statistical analysis applicable to dental and oral research. The kinds of studies we have considered and will continue to consider range from large scale field surveys to small scale clinical trials. The kinds of data we have considered and will continue to consider range from bona fide quantitative measurements to categorical ratings. We expect to apply in the future the kind of paradigm we have successfully applied in the past. Specifically, challenging statistical analysis problems are identified in an actual dental study, theoretical statistical research is conducted when necessary and the results of that research are applied to the original problem. Experimental designs developed to increase study efficiency in other disciplines will be adapted for use in basic oral biological research as well as in applied clinical and field investigations. The theoretical results would be (and indeed have been) published in a technical statistical journal, and their applications would be published in a dental journal. We plan to devote considerable attention to the analysis of multivariate data, both quantitative and discrete. We will give special emphasis to log linear and logistic regression methods for the latter kind of data.